count the number of times a string occurs in ElasticSearch documents

Question

I have a simple ElasticSearch question. Let me explain through an example:

If I have two ES documents, both with a field drinks, in which we store names of ordered drinks, how can I count the total number of each drink across both documents (drinks can repeat, since more than one person can order, say, Pepsi)?

So, if I have this:

document_1: drinks: Pepsi, Pepsi, Pepsi, Fanta, water document_2: drinks: Pepsi, Pepsi, Fanta

I want to build a bar graph that will plot total number for each of these three drinks across both documents:

Pepsi: 5, Fanta: 2, water: 1

What would be the simplest way to do this? Thanks :-)

p.s. All I was able to achieve was to show number of documents in which each drink occurs, so I will get back Pepsi: 2, Fanta: 2, water: 1, but I'm unable to count them all.